There is virtually no limit to "fun character that the game supports...won't break the game being too powerful or too weak and is well within the fluff..." that you can make without including the optional subsystem needing DM approval of Multiclassing.
Coming up with corner case after individual story of why a specific character needs a particular concession [using MC] does not change or disprove this. We can all come up with stories that can use it...Why is it impossible or so awful a prospect to imagine coming up with a character that doesn't need it?...and have that character still be considered "fun" and no more restricted in-game/story wise [other than by their array of class abilities] than one that does [multiclass]?
I agree with this sentiment (even though I allow multiclassing).
I guess I just can't relate to the idea of players
fixating on a certain character, and not being interested in trying a different one if it doesn't fit the campaign.
When I'm going to enter a new campaign as a player I
want the DM to tell me what he is going for in this campaign. I want to build a character that is perfectly suitable to that campaign--and since the DM is designing the campaign only he can tell me what that is. He might not understand my character concept at first, so I have no problem discussing it with him to see if he will reconsider once he understands the concept. But at the end of the day, he knows his campaign concept a lot better than I do.
If this is just the argument over whether players should have input into the nature of a campaign or not all over again, there is no answer. It's a matter of playstyle. I can enjoy either. But once you have that established for a specific campaign everything else needs to be based on that assumption. If players don't define the campaign then they make a character that fits or sit it out. Maybe they aren't mature enough as a role-player to get over a fixation with a certain character they want to play. Hopefully the DM or other players can help them brainstorm. If they really insist that they
must play a certain character in a DM-creation style campaign, and the DM says it doesn't fit, they are being completely unreasonable, and I am leery of having them in the group at all--even if I'm not the DM. (We have had this experience once. The DM conceded. It didn't make a positive contribution to the campaign.) My DM runs campaigns that are definitely DM-creation campaigns with a clear goal and image in mind of what that campaign is, and that are not about player campaign design input. Then he is often over-accommodating in allowing characters that aren't really good fits, and which he has to bend his concept to try to fit in. While allowing them hasn't ruined a campaign, it has never enhanced the play experience. They would have been better campaigns had he simply said, "look, that isn't what I'm running here, so let's do one of your other fun character ideas." I'll say further--I myself have played characters that haven't really fit a campaign all that well, because my DM was over-accomodating, and those characters have been much less fun than if I just picked something that fit. This is just now inspiring me to have a talk with him about setting more guidelines and restrictions for his next campaign to better preserve what he is going for.
So, if this is just an argument over a decision where the appropriateness is based
entirely on playstyle (and I'm thinking it has become that for some of the sub-arguments), that is a completely invalid argument and a waste of time.